Pulsation-preventing mechanism.



, S. A. MOSS. PULSATION PREVENTING MECHANISM? APPLICATION FILED FEB. 2. I917- Patented 001i. 8, 1918.

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Inventor;

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ETAEETFOBD A. MOSS, 0F LYNN, MASSACHUSETTS, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION 01 NEW YORK.

PULSATION-PREVENTING MECHANISM.

Specification or Letters Patent.

Application filed February 2, 1917. Serial No. 146,128.

3'0 all whom it may concern:

Be it known that I, SANFORD, A. Moss, a citizen 01"" the United States, residing at Lynn, in the county of Essex, State of Massachusetts, have invented certain new 'and useful Improvements in Pulsation-Preventing Mechanisms, of which the following is a The present invention relates to pulsation preventing means for centrifugal compressors, such as" air compressors. The object of the invention is to provide an improved arrangement for preventing pulsations in compressors, which arrangement is automatic in operation, simple to build, and easy to install, either on new machines or those already in use. The invention, while it is not necessarily limited thereto, is particularly intended for use in connection with compressors equipped with constant volume governors.

For a consideration of what I believe" to be novel and my invention, attention is directed to the accompanying specification and the claims appended. thereto.

In the accompanying drawing, Figure 1 shows a turbo-compressor unit equipped with a constant volume governor and with any improved pulsation preventing mechamam Fig-"2 is a detached side elevation partly in section of the pulsation preventing mechanism, and Fig. 3 is a top plan view thereof.

Referring tothc drawing, 5 indicatesn centrifugal compressor having an inlet con-- duit 6 and a discharge conduit 7. It is shown as being dm ven'by a steam turbine, a portion of which is indicated at 8. 9 indicates a valve mechanism which controls the and 17 the hand wheel for adjustingit along The fluid motor 10" the scale on beam 11. is also suitably connected to a speed gov.- oinOr 18 as shown. The operation of a constant volume governing mechanism as just described is well knowri. The weight 16 is set on the scale for the desired volume of flow and the float 13 acts on the beam 11 to tilt it so as to cause the fluid motor 10 to open and close the valve mechanism 9 to maintain the turbine S at the speed required Patented Oct. 8, 1918.-

to supply the volume of air desired. If the volume of air flowing tends to decrease then the float 13 lowers a little thus tilting the beam 11 and opening the valve mechanism 9 to admit more elastic: fluid to the turbine so as to increase the speed and thus cause the compressor to take more air. On the other hand, if the volume tends to increase then the opposite action takes place. The speed governor I8 is normally inactive, the turbine being wholly under the control of the constant volume governor, and only comes into play to take control in case of excess speed. It is somewhat of the nature of an emergency governor. The constant volume governing mechanism as just described is well known. and forms no part of the present invention, except that it may enter into the general combination. 19 is a by-pass conduit connected with the discharge side of the compressor and used for wasting air in order to prevent the occurrence of pulsations, this method of preventing pulsations being one which is now well known. In the present instance it is shown as connecting the discharge end of the compressor to the inlet end beyond the constant volume governor, this arrangement being a preferable one as it assures that all the air which is measured by the constant volume governor is utilized. Arranged in the by-pass conduit 19 is a swinging check valve 20 carriedby an arm 21 which is pivoted on a rod 22' journaled in the valve casing 23. This valve opens toward the inlet end of the compressor and is adapted to be opened'by the pressure existing upon the discharge side of the compressor. 24 indicates a stop for limiting the opening movement of the valve. The rod 22 projects well beyond the valve casing 23 at one side and has fixed thereon aframe 25 having a scale marked thereon and carrying an endless screw 26 adapted to be turned by the hand wheel 27, Sliding on the fra-u'ic 25 is a weight 28 having a threaded portion which engages the screw 26. By turning the hand wheel 27 the weight may be adjusted along the frame 25 as is obvious. The weight 28 acts to bias the valve20 toclosed position.

The point atv which pulsationsoccur in a centrifugal compressor depends upon the volume and pressure. In fact, it is now known to depend upon the volume divided by the square root of'the pressure, which may be termed theload coefficient of the machine. As long as the load. coefiicient keeps above a certain value pulsations will not occur, but when it reaches or fallsfbelow this value they may occur. The value of the load coeflicient at which pulsations coininence may be termed the critical value.

This critical value differs for different machines and can only be determined by experiment. With a machine equipped with a constant volume governor the volume delivered by the -machine remains constant. iVith such a machine, therefore, it will be evident that the critical value is directly a function of the square root of the pressure. In other Words, for every volume for which the constant volume gov rning mechanism may be set there is a pressure at v air from the delivery to the inlet side of the compressor.

What I claim as new and desire to secure by Letters Patent of the United States, is

1. The combination with a centrifugal compressor having a constant volume governor which may be set for the desired volume, of a by-pass conduit connected with the discharge side of a compressor, a valve in the conduit adapted to be acted on directly by the pressure in theconduit, said. pressure tending to open the valve, means connected with the valve which biases it toward closed position, and adjustable mezms'associated with said biasing means for increasing or decreasing the force of said biasing means whereby the biasing means may be set in ac cordance with the setting for the constant volume governor.

2. The combination with a centrifugal compressor having .a constant volume governor, 'of a by pass conduit connecting the discharge side of the compressor to the'inlct side, a valve in the conduit adapted to be acted on directly by the pressure in the conduit, said pressure tending to open the vabxe, a frame having a scale thereon connected with the valve, and a weight on the frame which acts to bias the valve toward closed position, said weight being adjustable on the scale sov that it may be set in accordance with the setting of the constant volume govt-zrnor.

3.- The combination with a centrifugal con'ipressor having a constant volume gov-- ernor, of a lay-pass conduit connected with the discharge side of the compressm', a

swinging check valve in the conduit adapted to be acted on directly by the pressure in the conduit, said pressure tending to open the valve, and means connected with the valve which biases it toward closed position, said means being adjustable so its biasing force may be regulated in accordanccivith the set ting of the constant volume governor.

at. The combination with a centrifugal compressor having a constant volume gov-- ernor, of a bypass conduit connecting the discharge side of the compressor t,o the inlet side, a swinging check valve in the conduit adapted to be acted on directly by the pro"- sure in the conduit, said pressure tending to open the valve, a frame having a scale thereon connected with the valve, and a weight on the frame which acts to bias the valve toward closed position, said weight being adjustable on the scale so that it may be set in In witness whereof, I have hereunto set my hand this 31st day of 5 111,191?

SANFORD A. MOSS.

, accordance with the setting of the constant volume governor. 

